The invention relates to a method for producing a dispensing device for coatable products, such as adhesive materials, in which a sleeve-shaped element, a pedestal with a spindle, a piston for receiving the product, and a closure cap are produced by injection moulding, and the thus-produced parts are subsequently assembled, wherein the piston is moulded to the spindle in a common injection-moulding process, and the piston and spindle are made to be separable after injection-moulding.
Dispensing devices of this kind, particularly for adhesive materials, i.e. so-called glue sticks, are represented in great numbers in the market. They usually consist of at least a sleeve-shaped element, a pedestal with a spindle, a piston for receiving adhesive material, and a closure cap. These components are each produced from suitable plastic material by injection moulding and are subsequently put together or assembled. The four components have to be individually movable relative to one another when assembled. The production cost for dispensing devices of this kind is obviously considerable, since a total of four different injection-moulding moulds are required for production of the four basic components, and correspondingly four respective injection-moulding processes are required. Moreover, assembly is also relatively costly, since all four components have to be fastened to another. Since the injection-moulding costs and the assembly costs represent the main part of the overall costs for dispensing devices of this kind, this form of manufacture is deserving of improvement.
A method for producing a dispensing device for easily spreadable products is known from EP-A-0 940 103, in which a sleeve-shaped element, a pedestal with a spindle, a piston for receiving the product, and a closure cap are produced by injection moulding, and the thus-produced parts are subsequently assembled. In this process the piston is moulded to the spindle in a common injection-moulding process and remains rigidly connected with the spindle in the assembled actuating setting of the dispensing device. Relative movement between piston and spindle is not possible. However, in the case of glue sticks, a relative movement of piston and threaded spindle has to be possible in order to be able to dispense adhesive.
It is the object of the invention to simplify the production and assembly of dispensing devices of that kind for coatable products. According to the invention this object is met by a method, of the kind described in the introduction, in which the piston is injection-moulded to the spindle such that the two components are separable after moulding.
In the method of the invention, one injection-moulding process and one tool are made redundant in comparison to the conventional mode of production, since the piston is injection-moulded directly to the spindle to form a single body of two separable parts. The connection between piston and spindle can be selected so that the piston and spindle can be separated in a simple manner after the injection-moulding process. In one embodiment, the piston is positioned on the spindle by rotation during assembly, whereby the connection between piston and spindle is destroyed. Thus, assembly also can be simplified substantially.
In order to simply assembly further, it is advantageous to connect the piston to the spindle by frangible, injection-moulded locations. It is then possible in simple manner to destroy the frangible locations by rotating the piston on the spindle. In that case, either the piston together with spindle and socket that are injection-moulded thereon can be knocked into the sleeve-shaped element and subsequently the piston screwed onto the spindle by destroying the frangible locations, or the piston can be initially screwed onto the spindle by destroying the frangible locations and then the thus-formed unit knocked into the sleeve-shaped element.
The production cost can be still further reduced if the spindle and piston are injection-moulded to the sleeve-shaped element in a common injection-moulding process. Here, too, the connection between the components in the common injection-moulding process can be selected so that this can be easily destroyed. In this embodiment at least one more injection-moulding tool is made redundant, whereby moulding cost is still further reduced, as well as assembly cost. This result is achieved advantageously by injection-moulding the spindle, piston, and sleeve-shaped element together by way of frangible locations connecting the parts.